netdev - Re: [PATCH 1/1] virtio_net: Add timeout handler to avoid kernel hang

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <430b899c-aed4-419d-8ae8-544bb9bec5d9@lunn.ch>
Date: Fri, 19 Jan 2024 18:29:28 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Heng Qi <hengqi@...ux.alibaba.com>
Cc: Zhu Yanjun <yanjun.zhu@...ux.dev>, Paolo Abeni <pabeni@...hat.com>,
	Zhu Yanjun <yanjun.zhu@...el.com>, mst@...hat.com,
	jasowang@...hat.com, xuanzhuo@...ux.alibaba.com,
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
	virtualization@...ts.linux.dev, netdev@...r.kernel.org
Subject: Re: [PATCH 1/1] virtio_net: Add timeout handler to avoid kernel hang

> > > >       while (!virtqueue_get_buf(vi->cvq, &tmp) &&
> > > > -           !virtqueue_is_broken(vi->cvq))
> > > > +           !virtqueue_is_broken(vi->cvq)) {
> > > > +        if (timeout)
> > > > +            timeout--;
> > > This is not really a timeout, just a loop counter. 200 iterations could
> > > be a very short time on reasonable H/W. I guess this avoid the soft
> > > lockup, but possibly (likely?) breaks the functionality when we need to
> > > loop for some non negligible time.
> > > 
> > > I fear we need a more complex solution, as mentioned by Micheal in the
> > > thread you quoted.
> > 
> > Got it. I also look forward to the more complex solution to this problem.
> 
> Can we add a device capability (new feature bit) such as ctrq_wait_timeout
> to get a reasonable timeout？

The usual solution to this is include/linux/iopoll.h. If you can sleep
read_poll_timeout() otherwise read_poll_timeout_atomic().

	Andrew